Log messages improvements in ACL code:
  * log levels: if the message is an error, use LOG_LEVEL_ERR
  * Give the ACL context in messages where it was missing
  * Give the ACL function error message when possible
  * Clarifications: permset -> permissions set, ...
Log messages improvements in cf-agent code:
  * Consistent output format
  * allclasses.txt: if an error occurs, give its full path and the fopen() error message
  * Minor cosmetic changes
Log messages improvements in internal DB code:
  * Message for every OpenDB(),NewDbCursor() failure
  * Consistent description of databases
  * Include database path in error messages
Log messages improvements in various places:
  * LOG_LEVEL_ERR instead of VERBOSE when a file could not be opened
  * More context for some messages
Log messages improvements in cf-key:
  * More context for some messages (public/private key, filename, ...)